I bought an SSD and I want to have my partitions aligned to 2048KB for better performance. I'm wondering, is it possible to realign the partitions without losing data? Is there some program that does this?

The problem with what you are trying is that the partitions both need to begin and end on a multiple of 2048kb, which is easy with any partition tool (partition magic, or gparted) and the allocation unit size, which is set when the partition is formatted, while their is data in place.

So pretty much no. To align the partition you can do without reformatting, but to reset the allocation unit size you need to reformat.

I've done this several times with GParted on regular hard drives. The warnings were always defrag first (I honestly don't know if you can do that), then best of luck and no guarantees. I never had a problem, but I was always aware I might. If you have data you want to keep it's best to just make a backup, try repartitioning, then you can test to see if your data is intact. If not you have a backup to begin rebuilding with.

How would you align them with losing data anyway?
–
BenderNov 5 '09 at 23:12

1

This answer is actually incorrect. You should still backup your files, but as numerous other people have pointed out, you can use gparted or even a specialized tool such as Paragon's alignment tool (paragon-software.com/home/partition-alignment/index.html) to physically shift the partitions without losing your data.
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robMay 13 '12 at 5:48